EPA/530/SW-587d
MAY 1977
at
-------
RECOVERY OF LANDFILL GAS AT MOUNTAIN VIEW
Engineering Site Study
This final report (SW-587d)
on work done under grant no. S803396 01
was prepared by John A. Carlson
U.S. ENVIRONMENTAL PROTECTION AGENCY
1977
-------
AC KNO WL EDGME1 T
I wish to thank the persons who have ,oykedwith me.and made this
report possible; namely, Richard Haughey, Robert McCafferty, and
Don Powell.
—J.A.C.
This report was prepared by the City of Mountain View, Calif.
under grant no. S803396 01.
An environmental protection publica ion (SW 587d) in ‘the solid waste
management series. Mention of con’iiierciai prodücts does not,.constitute
endorsement by the U.S. Government. Editing and te hhicai Content of this
report were the responsibilities of the Systems Management Division of the
Office of Solid Waste.
Single copies of this publication are available from Solid Waste
Information, U.S. Environmental Protection Agency, Cincinnati, Ohio 45268.
-------
TABLE OF CONTENTS
Chapter 1. Introduction Page No .
Project Objective
LocaFe and Background
Approach 3
Chapter II. Conclusions
Landfill Gas Composition-Static 5
Conditions
Withdrawal Rate/Radius of Influence 5
and Landfill Gas Composition
Total Gas Production Rate 5
Effect of Moisture 5
Chapter III. Discussion of Results
Landfill Gas Composition-Static Condition 6
Withdrawal Rate/Landfill Gas Composition 7
Withdrawal Rate/Radius of Influence 9
Total Gas Production Rate 10
Accuracy 11
Chapter IV. Implementatio , Testing, and Operation
Design versus As-Built 12
Construction
Testing 12
Equipment Maintenance 12
Chapter V. Analytical Procedures
Sampling (Monitoring) 13
Analyses 114
Chapter VI. Plates and Pictures
Plate 1 - Well Locations 17
Plate 2 - Well Locations - sectional view 18
Plate 3 - Well Cross Sections 19
Plate 4 - Distribution of Gas - Methane, before 20
Plate 5 - Distribution of Gas - Methane, after 21
III
-------
Page
Plate 6 —
Plate 7 -
Plate 8 -
Plate 9 -
Plate 10
Plate 11
Plate 12
Plate 13
Plate 14
Plate 15
P1 ate
Plate
P1 ate
Plate
Plate
Picture
Picture
Picture
Picture
PART
PART B
PART (;
PART 0
PART E
PART F
22
23
2 1+
25
26
27
28
29
30
35
42
‘43
‘+4
45
46
L47
48
49
50
52
54
55
59
60
61
Distribution of Gas - Carbon Dioxide, before
Distribution of Gas - Carbon Dioxide, after
Distribution of Gas - Nitrogen, before
Distribution of Gas - Nitrogen, after
- Distribution of Gas - Oxygen, before
- Distribution of Gas - Oxygen, after
- Distribution of Gas - Methane movement
- Distribution of Gas - Nitrogen movement
- Long Range Continuous Gas Withdrawal Chronology
through 20 - Head Loss Curves
21 - Pressure Diagram - Gas withdrawn at middle of landfill
22 - Pressure Diagram - Gas withdrawn at bottom of landfill
23 - Head Loss Curve - General
24 - Discharge Rating Curve
- Accuracy of Results
1 - Pump Station
2 - VolkswagOfl Engine and Pump
3 - Monitoring Board
4 - Burning Stack
Appendix
A - Problems, Delays and Changes
- Data
- Gas Dynamics in Refuse Landfill
- LO-OX Induction System
- Costs
— Calculations
Chapter VII.
-------
INTRODUCTION
Project Objective
The objective of the project was to determine how much methane gas can be
withdrawn from a shallow sanitary landfill at a suitable quality and quantity
to make it economically feasible for commercial use. The site of the sanitary
landfill is Shoreline Regional Park in the City of Mountain View, California.
The typical depth of the landfill is 40 feet.
Locale and Background
The City of Mountain View in 1966 designed a 550-acre regional park in an
area comprised mainly of flood plains, a sewage treatment plant, dumps, a pig
farm, and a car-wrecking yard. The proposed park would replace the existing
eye sores with a pleasingly aesthetic recreational park. The park landfill is
comprised of 250 acres of sanitary landfill, 175 acres of earthfill (dikes,
building pads, and roadways), 75 acres of lakes, and 50 acres of wildlife
refuge. The refuse capacity of the site is 4,000,000 tons. Plate 1 shows the
configuration of the landfill.
In the Shoreline Regional Park sanitary landfill, organic and inorganic
refuse is placed in chambers that are lined with 5 feet of clay seal (10’
cm/sec permeability) on the sides and bottom. The refuse Is compacted to 1,200
lbs/cubic yard and covered daily with a minimum of six inches of dirt. The
final lift is covered with one foot of compacted clay soil plus a minimum of
one foot of top soil. The bacteria, as they consume the organic material in
the refuse, produce gases as waste products. With sufficient moisture, during
the first year of decomposition, a relatively high proportion of oxygen in the
fill promotes aerobic decomposition, which produces carbon dioxide, minimizing
the production of methane. But, with time, as anaerobic conditions prevail,
methane and carbon dioxide, with traces of other gases are produced in greater
proportion. The concern for landfill gas arises from the potential hazard of
methane accumulation and the ability of carbon dioxide to affect the quality
of a water supply. Methane is a colorless, odorless hydrocarbon (C l - i 4 ) pro-
duced by biological decomposition of organic matter. Also known as marsh gas
and in coal mines as firedamp, methane can be used as fuel or as a raw mate-
rial in chemical synthesis. Alone, methane is not explosive, but when it
accumulates at concentrations of 5 to 15% in air it is highly explosive.
Since oxygen is virtually void in a densely compacted and sealed landfill when
methane is produced, there is no danger of the fill exploding. However, if
methane moves through the soil and accumulates in structures, it may cause
explosive conditions.
Methane migrating through the sides or top of landfills may adversely
affect plant life. Where disposal sites are located next to planted areas, or
where parks and recreational areas are planned after disposal operations cease,
the affect of methane on plant life is of particular concern.
Capturing landfill gas takes resource recovery another step beyond recla-
mation that is now carried out at a transfer station where metal, glass, and
paper are recovered and recycled. Across the Country, there are many landfills
that are sources of untapped energy. With each new landfill that is opened,
-------
a new source of energy is created. How these landfills are designed and how
recovery wells are placed during the fill process can well affect the rate of
recovery and total yield of each fill and, ultimately, the amount of energy
available.
This report investigates the viability of producing methane gas from a
shallow sanitary landfill. By measuring the landfill gas composition, gas
withdrawal rates, decomposition temperature, pH, and the pressures within the
refuse, this project attempted to provide the composition and quality of the
landfill gas, optimum gas withdrawal, well spacing and gas withdrawal rates,
potential gas production rate, and the affect of varying the water moisture
content of the refuse on the gas production.
As part of the original proposal for the project, a section was included
on the marketability of the landfill gas. But, it was decided that this study
would be separate from this report. As a result of this project, a contract
to sell the landfill gas to a utility company, Pacific Gas and Electric Com-
pany (PG&E), was executed.
2
-------
Approach
The project had three phases. In Phase 1, the project called for deter-
mining the effect of gas withdrawal rates on gas composition and the optimiza-
tion of withdrawal rate for long-term production. In Phase 2, the Mountain
View site was studied, in light of the data generated in the first phase, to
determine total yield, production costs, and revenues (this phase was subse-
quently deleted from the project). En Phase 3, the effect of moisture and
other factors upon gas production rates from the sanitary landfill was to be
studied. This phase was discontinued at the time this report was finalized.
For Phase 1, the method used to obtain the above mentioned results was:
a. Construct two gas withdrawal production wells, designated 7A
and 7B, In separate refuse chambers as shown on Plate 1. Each
gas withdrawal well has two levels from which the gas was drawn,
i.e., one from the bottom and the other from the middle of the
landfill. The piping lead into a positive displacement pump
which was belt—driven by a Volkswagon engine. The gas was dis-
charged through a demister into a burning stack.
b. Construct 14 pressure monitoring wells around withdrawal well
7A and 16 pressure monitoring wells around withdrawal well lB as
shown on Plates 2 and 3. Each pressure point in each refuse cham-
ber (28 for withdrawal well 7A, and 20 for withdrawal well 7B)
was connected to a central monitoring board located in the com-
pound area of the pump. The monitoring board simulated the field
condition to minimize recording errors, and each pressure point
had a separate valve which led to manometers.
c. Pump gas from the withdrawal wells at varying rates for a
short period of time, and measure the composition of the gas and
the pressure distribution in the landfill. The gas, over dif-
ferent time periods, was withdrawn from the bottom only, the mid-
dle only, and both the bottom and middle levels in the landfill.
For the testing procedures used, refer to Chapter V. “Testing
Procedures.”
d. Once the optimum pumping rate was established, the well was
continually pumped for 30 days to confirm the rate established
by the short-term pumping. The gas was sampled at least twice
a week to track the gas constituents.
For Phase 1, withdrawal well 7A was used as the primary source of infor-
mation. Withdrawal well 7B was used to confirm the information obtained in
well 7A.
For Phase 3, the method used to determine the effect of moisture on the
landfill was essentially the same as Phase 1. Both withdrawal wells
1A and lB were constructed exactly like well 7A and the refuse around well 1A
was moistened with water.
3
-------
Production well lA was manipulated to determine the effect of moisture.
Production well lB was used as a control. Using the optimum withdrawal rate
found in Phase 1, both wells were pumped for one week and the gas analyzed.
This test was the basis for recording changes in the two wells over the test-
Ing time period. Water was then added to the refuse surrounding production
well 1A equivalent to 10% moisture content of the refuse. The gas from both
wells was constantly analyzed to determine the amount and timing of the effect
of moisture of the refuse. At this point, it was determined that groundwater
was entering the landfill at a different location in the landfill, and this
phase of th,e project was discontinued. See Plates 1 through 3 for well cross
sections and locations. Refer to Chapter V “Testing Procedures” for testing
methods.
k
-------
COWCLtJS IONS
The following are the basic results of the program. If the reader intends
to use these results, it Is suggested that Chapter III, “Discussion of Results”
be read in order that the results are correctly applied.
Landfill Gas Composition-Static Conditions
The composition of the landfill gas during static conditions varied in
each part of the landfill. Table 1 depicts the variation in the gas composi-
tion in the landfill. The samples in Table 1 were taken prior to initiation of
this project.
TABLE 1
WELL 7A
VARIATION IN LANDFILL GAS COMPOSITION
STATIC CONDITION
AT START OF PROJECT
Percentageof Constituents of Different Samples
Weilpoint Identification 7A-M6D 7A-SM7 7A-SM4 7A-M7D
Methane 61.69 4’.65 23.52 3.18
Carbon Dioxide 37.00 36.50 29.92 4.73
NItrogen 0.74 16.48 44.75 72.59
Oxygen 0.54 1.37 1.80 19.50
MiscellaneOus 0.02 0.01
*Refer to Plate 2 for weilpoint locations.
Withdrawal Rate/Radius of Influence and Landfill Gas Composition
A stable gas composition (44% Methane, 34% Carbon Dioxide, 21% Nitrogen,
and 1% Oxygen) was obtained at a withdrawal rate of 50 cfm for a well 40—feet
deep. The effective radius of influence for 50 cfm is approximately 130 feet.
Total Gas Production Rate
The estimated total gas production rate, 150—acre site, 40-feet deep,
Is 7.5 nrcfd. Refer to Part F, “Calculation,” of the Appendix for ca1cu1atiofl
or determining the total gas production rate.
Effect of Moisture
Project was terminated too early to notice any affect. Groundwater was
Infiltrating into the landfill and was affecting the monitoring and pumping.
5
-------
DISCUSSION OF RESULTS
Landfill Gas Composition-Static Condition
For the major portions of the landfill tflat were tested, the analysis
showed the landfill was undergoing anaerobic decomposition. There were pockets
that contained primarily air randomly spaced throughout. These pockets might
have been due to an excessively dry section of refuse or might be a result in
an error in the sampling procedures. Static condition samples were taken prior
to and after withdrawing gas from the landfill at rates of lOOcfm, lSOcfm,
200cfm and 300cfm. The pumping was done from December 16, 1974 to January 7,
1975. The static condition tests were taken on December 13, 174 and January 17,
1974. Please refer to the section “Data’ 1 of the Appendix for gas analyses for
all static condition tests.
Plates 4 through 13 show the change in the distribution of gases in the
landfill from December 13, 1974 to January 17, 1974. These Plates show that
the landfill gas was drawn down and horizontally into the well. Inspection of
the nitrogen and oxygen concentration on Plates 9 and 11 reveals the intrusion
of air into the landfill at the higher withdrawal rates.
After withdrawal of gas, as a result of the short run tests, it appears that
the concentrations of methane and carbon dioxide decreased and nitrogen and
oxygen increased. From Table 2 it can been seen how the gas concentrations
changed.
TABLE 2
AVERAGE CHANGE LANDFILL GAS COMPOSITION
DUE TO PUMPING
Mean Range Wherein
Constituent Va lue* 99% of Readings Lie
Methane: Before** 45% 27-63
After ** 44% 30-59
Carbo n Dioxide: Before 35% 27—42
After 32% 25-40
Nitrogen: Before 18% 0-41
After 21% 2-40
Oxygen: Before 1.7% 0.1-3.2
After 2.1% 0.1-4.0
*Two samples, 7A-M5D and 7A-M7D, from before and three samples, 7A-M25, 7A-M4S,
and 7A-M7D, from after are omitted from calculations due to probability of air
contamination. Values in the Table were obtained by using the data from the
analysis of the samples taken at static conditions before and after the short
run testing.
t*Refers to values taken before or after the short run tests.
6
-------
Since the methane and carbon dioxide paralled each other, it is assumed
that the landfill never reverted to the aerobic state. Under aerobic condi-
tions, the carbon dioxide would have increased considerably and the methane
would have decreaed to approximately zero. Intrusion of air Into the landfill
apparently only retarded the anaerobic decomposition. There might be two rea-
sons for this. For one, the top soil and clay seal could have absorbed suffi-
cient oxygen as the air passed through them such that the remaining oxygen was
not enough to affect the anaerobic decomposition. On Plates 9 and 11, respec-
tIvely, It can be seen that the nitrogen content increased substantially at
the top of the landfill and there was only a minor change in the oxygen content.
The other reason is that the majority of organisms in the landfill (at least
near the top of the landfill) might be facultative due to the continuous pas-
sage of air and landfill gas in and out of the landfill as the atmospheric
pressure changes. (Please refer to section “Gas Dynamics In Landfill” in the
Appendix for a discussion on the porosity of the top clay seal and the affects
of atmospheric pressure on the landfill.) The facultative organisms could tol-
erate the oxygen being drawn In by the pumping and would Immediately recover
to anaerobic decomposition when the pumping was discontinued after they util—
Ized the oxygen in the landfill.
Withdrawal Rate/Landfill Gas Composition
The gas composition varied as the withdrawal rate varied not due to
exceeding the gas production rate by the anaerobic organisms, but due to the
intrusion of air through the top clay seal of the refuse landfill. Plate 14
shows the variation In landfill gas composition as the gas was withdrawn at
different rates. From Plate 14, It can be seen that a stable condition was
reached at a withdrawal rate of 50 cfm. Table 3 gives the values for methane,
carbon dioxide, nitrogen, and oxygen gas for every test taken during the time
the gas was withdrawn at 50 cfm. Table 3 also gives a running average of
values.
By inspecting Plate 14, the reader can see the interrelationship between
the four major gas constituents. In general, methane and carbon dioxide
paralled each other and decreased as the withdrawal rate increased. Nitrogen
and oxygen Increased as the withdrawal rate increased. Proportionately, the
amount and variation of nitrogen was much greater than ox,ygen.*
* In air, the ratio of nitrogen to oxygen is approximately 4 to 1. In the
landfill gas, the ratio of nitrogen to oxygen varied but was approximately
20 to 1. The difference In ratios apparently means that as the air was
drawn through the top soil, clay seal, and refuse, the oxygen was absorbed
by these media and/or removed by microorganisms In the landfill.
7
-------
TABLE 3
50 cfm Continuous Pumping
35. 75/35.75
N
+
May
22 4h42141.42*
21.89/21.89
0.94/0.94
May
23 42.20141.81 36.80/36.28
20.00/20.95
0.90/0.92
May
27 43.70/42.44 33.60/35.38
21.30/21.06
1.40/1.08
May
28 41.68/42.25 33.57/34.93
23.41/21.65
1.34/1.15
May
29 41.38/42.08 33.42/34.63
23.51/22.02
1.69/1.25
June
5 45.44/42.64 34.86/34.67
19.10/21.54
0.60/1.15
June
6 45.65/43.07 31.66/34.24
21.40/21.52
1.28/1.16
June
11 44.50/43.25 34.64/34.29
20.22/21.35
0.64/1.10
June
13 45.25/43.47 34.65/34.33
19.38/21.13
0.72/1.06
June
17 45.47/43.67 35.03/34.40
18.98/20.92
0.52/1.0
June
20 46.49/43.93 30.73/34.06
21.34/20.96
1.44/1.04
June
25** 45.84 19.4
29.7
5.22
June
27 44.92/44.01 35.02/34.14
19.5a/20.84
0.48/1.0
June
30 44.31/44.03 34.82/34.20
20.39/20.81
0.48/0.96
*
Data/Running Average
**
Sample not Included in calculations due
is contamination of the sample.
to high air content
Probable cause
***
For ease and speed of analysis Argon was
Argon content is negligible.
not separated from
Oxygen. The
8
-------
At the withdrawal rate of 200 cfm, sufficient amounts of air were drawn into
the landfill, as indicated by the increase in nitrogen from February 11, 1975
to March 2, 1975. By March 2, 1975, a sufficient amount of air was drawn into
the landfill to affect the anaerobic condition of the landfill and it took 51
days for the landfill to recover.
On March 17, 1975, the withdrawal rate was reduced to 150 cfm. But, after one
day, it was found that the landfill had not recovered and pumping was discon-
tinued until April 23, 1975.
On April 23, 1975, the pumps were started at a withdrawal rate of 100 cfm.
After eIght days, the gas quality showed signs of deterioration. By 13 days,
May 5, 1975, the quality was definitely down and the withdrawal rate was reset
at 75 cfm on May 6, 1975.
At 75 cfm, the gas quality appeared to go down slightly. It was difficult to
tell exactly what was happening since the PG&E gas chromatagraph was not work-
ing right and only partial results were being received. Refer to the Commen-
tary on Plate 14. A different lab was used and the first results back for
May 16, 1975, showed a drop in gas quality and the pump was stopped until
May 17, 1975 where the pump was restarted at a withdrawal rate of 50 cfm.
In view of the tests before and after the test taken on May 16, 1975, and since
this was the first sample taken by this new lab, the results of the sample taken
on May 16, 1975 may indicate a poorer gas quality than which existed. This may
mean that a withdrawal rate of 75 cfni might have produced a consistent gas qual—
I ty.
The withdrawal rate of 50 cfm, set on May 19, 1975, provided a consistent gas
quality of 44% CH 1 , 34% C0 2 , 21% N,,, and 1% 0,,. Refer to Table 3. As the
gas was pumped frOm May 19, 1975, to June 30,1975, the gas quality was actually
Improving as indicated by the running average values in Table 3.
Withdrawal Rate/Radius of Influence
The gas withdrawal rate was varied from 0 to 300 cfm as shown on Plate 14.
Plates lb through 22 show the pressure distribution in the landfill at dif-
ferent rates and withdrawal levels. The curves were derived by plotting the
measured pressures from the monitoring wells as shown on Plate 2. At first,
the flow rate was determined by using the pump curve for the positive displace-
ment pump. But the curve was too Inaccurate at the low flows, so the graph in
Plate 24 was established. Thereafter, consistent results were obtained for all
flows, especially below 75 cfm, by establishing the appropriate negative pres-
sure in the well for the desired flow rate. Plate 23 shows the relationshiP
between the negative pressure head and radius of Influence. The curve is a
generalized formula, see formula (1) below, derived from the data.
9
-------
Withdrawal rates above 200 cfni have a slightly greater radius than indicated
by the curve and withdrawal rates below 200 cfm have a slightly smaller
radius than indicated by the curve. Plate 24 shows the relationship between
the negative pressure head at the well and the withdrawal rate. By combining
the empirically derived formulas in Plates 23 and 24, i.e.,
If h
12.5/R 125 , Plate 23 (1)
and if = - O.00039Q (Q + 133), Plate 24 (2)
then hR 125 = - 0.004875 Q (Q + 133) (3)
The graph on Plate 25 shows the relationship between the withdrawal rate
and radius of influence for different pressure contours in the landfill. As
can be seen by Plates 23 and 25, there is no definite theoretical cut—off point
where the well does not affect the landfill and natural phenomena prevents
accurate field measurement. By using the chart in Plate 25, a negative 0.1
Inches of water pressure was established for the effective radius of influence.
At less than negative 0.1 inches of water pressure, the flow of gas is suscep-
tible to varying localized pressure fluctuations due to atmospheric pressure
changes and varying decomposition activity. These localized pressure fluctu-
ations would direct the gases away from the well.
Total Gas Production Rate
The estimate for gas production of the entire site will be based upon the
results of the long—term pumping of the landfill and the resulting radius of
influence. From Plate 14, it can be seen that a flow of 50 cfm provided a sta-
ble and slightly increasing methane content at approximately 44% (Table 2).
Plate 25 pictorially shows that at negative pressures between 0.5 and 0.1
Inches of water pressure, the pressures fluctuated and were influenced by
external phenomena; and that at negative pressures above 0.1 inches of water
pressure, the pressures were too small and erratic to measure accurately.
Therefore, It was assumed that an effective radius of influence that could be
used to space the wells and determine the total gas production would be where
the head of negative 0.1 inches of water pressure is as determined by formula
1 on Plate 23 and formula 3 on this page. Using formula 3, wIth the withdrawal
rate (Q) equal to 50 cfm and the head } h) equal to negative 0.1 inches of water
pressure, the radius of influence is approximately 130 feet.
If the wells are spaced at the apex’s of equalateral triangles whose dis-
tance from the apex to the intersection of the perpendicular bisectors is 130
feet, the distance between the wells is approximately 225 feet. Using this
spacing, a calculated withdrawal rate per acre is 99.2 cfm. With an effective
surface area of 150 acres of landfill, and this well configuration, the total
site could produce 10.3 im cfd at 44% methane gas. Refer to Part F, “Calcula-
tions,” of the Appendix for calculations.
TO
-------
Accu racy
The accuracy of the data depended upon our ability to maintain a constant
gas withdrawal rate, measure the actual pressures within the landfill, obtain
gas samples and analyze the samples. The positive displacement-type pump was
chosen so that minor pressure fluctuations in the landfill and atmosphere would
be negated and the withdrawal rate would only depend on the speed of the pump.
It was difficult to keep the Volkswagon engine which drove the pump by belts
at a constant speed. The horsepower required by the pump was negligible com-
pared to the horsepower output of the engine so that the engine was essentially
under no load. The engine had to be checked at least twice a day and the
engine adjusted if the speed was not right.
The pressures in the landfill were measured by manometers through 1/4-inch
tubing that were as long as 250 feet. Accurate and consistent results were
obtained until water from the gas started getting into the tubing. The water
had to be constantly forced out of the tubing with air pressure before the
pressure readings could be taken. Pressure readings above negative 0.1 inches
of water pressure were difficult to measure because the pressures were always
changing, probably due to atmospheric and decomposition rate fluctuations, and
the readings could not be duplicated exactly. For pressure readings from nega-
tive 0.1 inch to negative 0.5 Inches of water pressure, the majority of the
readings were steady but could not be duplicated after a couple of hours. For
pressure readings below negative 0.5 inches of water pressure, the readings were
consistent.
The gas sampling and analysis accuracy was very good. A bad sample was
easily noticed by the presence of high air content, over 5%, and could be dis-
regarded.
ii
-------
IMPLEMENTATION, TESTING, AND OPERATION
Design versus As-Built
Since there were many unknowns and variables associated with the project,
the design incorporated flexibility and sizing sufficient to handle the maxi-
mum withdrawal rate of 200 cfm. Only minor changes had to be made from the
original design.
Construction
No major problems occured during construction. By using a 36-inch auger,
the wells were easily drilled without any delays. It was difficult to keep
the piping straight in the well since the well had to be backfilled by drop-
ping 3’ rock and clay Into the well. But since the pipes did not have to be
straight to withdraw gas, the procedure was satisfactory.
Testing
As part of the project, Pacific Gas and Electric Co. analyzed the gas
samples and they supplied syringes to take the samples. No problems occurred
in taking the samples at positive pressure locations. Considerable care was
necessary if a sample had to be taken at a negative pressure point.
There was some problem in receiving results in sufficient time to make
corrections in the operations. This was no fault of the sampling or analysis.
It took time to conduct the analyses, and when the gas composition was changing
rapidly we could not keep up with it.
Equipment Maintenance
The only high maintenance items were the Volkswagon engines. A spare
engine was always kept on hand. A lower maintenance engine or electric motor,
though more expensive, would have provided a more continuous and consistent
operation.
When the engines were running on the landfill gas, the spark plugs fouled
faster than on gasoline and the carburator would ice up during the night. A
shroud had to be placed over the engine to keep the carburator warm enough so
that icing would not occur.
Our experience shows that a less refined combustion engine or electrical
motor would have been better for driving the pumps.
12
-------
ANALYTICAL PROCEDURES
The following were the standard sampling procedures used.
Sampling
The pH was determined by taking a beaker of water from the demister on the
positive pressure side of the pump. The pH was measured with an electronic
direct reading instrument, 0.2 graduations, 0.05 accuracy. A CENCO laboratory
pH meter, Catalog No. 21660, was used.
The temperature, measured in degrees Fahrenheit, was measured from a ther-
mometer located In the well casing immediately above the ground. The ambient
temperature was measured in a location that was away from the pump station.
The pressure within the landfill was measured via a 1/4-inch plastic tube
which was run from each pressure point in the landfill to a central monitoring
board located in an enclosed metal building. Each tube had a separate on/off
valve. All the valves were connected to a slant tube manometer, 0.20-0-3 inches:
water, 0.01 increffientS, and slant tube manometer which read up to 72 inches,
0.1 inch increments, water. Each pressure point was measured by turning on
the appropriate valve and reading the manometer. Dwyer manometers were used,
Model Nos. 2C9 and 211-72.
To determine the methane gas content of the landfill gas, a gas sample
was taken from the valve and sampling tube on the positive pressure side of
the pump. The sample was taken with a syringe by Inserting the needle into
the tube and allowing the gas pressure to force gas into the syringe. The
syringe was purged at least once. A “PLASTIPAK” disposal syringe order No.
3663, 50 cc capacity, LUER-LOK tip, was used.
Monitoring
All the pressure points in the landfill were lead onto a monitoring board
via 1/4—Inch plastic tubing and each point had a separate on/off valve. The
pressures could be read on a manometer by consecutively opening and closing
each valve. The system worked fine until water from the gas started building
up In the tubing. Additional time had to be spent clearing all the lines with
air pressure before the pressures could be read. There were two manometers,
a 72—Inch manometer and a 3-inch manometer. Each manometer was connected to
the monitoring board by a valve.
‘3
-------
Analyses
For Phase 1, the original procedure used to determine the optimum methane
gas production rate was to start out at a high withdrawal rate and steadily
reduce the rate twice a week until an acceptable methane content was reached.
Once that rate was established, the landfill would be pumped for 30 days to
confirm the initial methane content.
As Plate 14 depicts, the initial withdrawal rate of 200 cfm was too high
and had to be reduced to eventually 50 cfm before a consistent methane content
was reached. This meant that the initial procedure to establish theoptimun
production rate was too short to depict the capacity of the landfill. A period
of a week seems more advisable for the length of time at each pumping rate,
At least twice a week the following should be recorded: temperature (ambient
and gas), atmospheric pressure and pressure In all monitoring wells and produc-
tion wells.
From the second interim annual report of the Sonoma County Refuse Tests
Cells , Solid Waste Disposal Demonstration Grant, Project G06-EC-0035I, pre-
pared by EMCON Associates, it was shown that the leachate pH was contaminated
by soluable gases, especially carbon dioxide, and the pH remained around 5.
Therefore, the pH should be sampled once from each production well. During
the pumping, a complete analysis of the gas should be made twice a week.
For Phase 3, the procedure used to determine the effect of moisture con-
tent was to take the optimum rate established in Phase 1 and continually pump
the wells lA and lB while adding water to only the refuse surrounding well 1A.
The temperature (ambient and gas), atmospheric pressure, and the pressure In
all monitoring wells and production wells were recorded, and a complete analy-
sis of the gas was made twice a week. After running the pump station for 2
weeks, sufficient water was added to the refuse around well 1A to raise the
moisture of the refuse by 10%. If the project had not stopped at this point,
for every 2 weeks 10% moIsture would have been added until 60% moisture was
reached.
Analyses of the gases drawn from wells at the landfill were made both
on-site and in the laboratory. The on-site analyses covered the Identifica-
tion and quantification of sulfur compounds; the laboratory analyses include
the hydrocarbons and fixed gases.
The on-site analyses for sulfur compounds were performed by the PG& E
Department of Engineering Research personnel using an Austin Gas Titrator.
This instrument has the capacity of analyzing for sulfur compounds in the
following classifications: hydrogen sulfide, mercaptans, sulfides, and disul-
fides. This instrument does not have the capability of identifying Individual
sulfur compounds such as methyl or ethyl mercaptan, but through selective absorp-
tion techniques, identifies mercaptans as a group.
1k
-------
The laboratory analyses were accomplished on a Beckman GC-4 gas chromato-
graph using a three column configuration and a thermal conductivity detector
operating at 80 degrees centigrade column temperature. Oxygen-argon, nitrogen,
carbon monoxide, and hydrogen were separated and determined quantitatively
using an 8-foot by 3/16-inch molecular sieve 5A column. A 16—foot by 3/16—Inch
Porapak Q Column was used to separate and quantitatively determine methane,
carbon dioxide, ethane, ethylene and water vapor. Hydrogen, if present in
relatively low concentrations, can be determined quantitatively with this col-
umn. Hydrogen sulfide, if present in quantities greater than 100 parts per
million, can be determined using a 30-foot by 3/16-inch silicon 200/500 on
Chromosorb P Column.
15
-------
PLATES AND PICTURES
16
-------
1000 0 1000 2000 3000
SCALE IN FEET
Levee
Areas to be excavated
prior to sanitary fill
Areas to receive sanitary fill
without prior excavation
Area of fill with demolition debris
-------
60’ _______
H J 75 j
ALe cz d to dctvtni. Lne
head o64 cwtve., a.nd ohow
di .6tnJbu .t4,ofl O 9a.6e4
7A IA & lB
200
WELL LOCATIONS**
sectional view
Well Designation
** fer to Plate for well locations En landfill
***Well point designations. Example for well 7A, asterisked monitoring
point would be 7A-M2M
— -
Pump
StatLon
‘—ShaUow
Mon toning
We.U
‘-3
SHORELINE REGIONAL
PARK
-------
Peep
Sha.Uo ti
• ‘ . •: ‘
A ’d £
A’ - > V 4
,..g. ‘ .
IL
L r .. V
7 7 , , >V
7 L ç
3 ftL 4 ‘ ‘f l v ’ .
L # - V . ‘ .7’
73 L j
V £ >
A ‘
J . V 7 V,g AL
3 ‘. V - -
7 ,71 ç 7 ’Jç
V A V r A V A 14’
p,. r
p¼ &- L 3 V 4 -
‘J ,
l 4
“ “A F I ’
1> LVr ’ , •1 - -
, r A.
( Ag I V j L. t V V
( • AL r
7 )
‘<
I-
1 L. ‘-
L. - 3 . -‘ k 1 r1g
_, - )
A Lç - r,ç 1 1 C
1 .
V AV J&. . 1 ,c S.
7 A 3 1 A Al
S.
S. AL4 7 )V
‘Vt
l - r I
4(7
C
. sd 4. )V
V .
c •
L. r . -
Hole size
‘ pipe -
3/4” pipe
spacing
½” @ 6” spacing
- 1/4” @ 6” spacing
SHOREL INE REGIONAL PARK
WELL CROSS SECTIONS
( t\
Pwda .tJ .o ’t MonLton ng Mon to’ ng
(Ue U WeLt.
6” PVC 3/4” PVC 3/4” PVC
• t._ ‘I
0*
C
7
I
Ic
4<
,
i,•Il
Ir#*
s —
4
.7
‘9
I
-7
.7
V
A
S.
4’
CLay i” -/ ’
3” RocI ;i (
Re u o (>
it //
- .‘
19
PLATE 3
-------
D
B
p
T
H
0
F
C
£
L
L
Yr)
1,
- - PARK
100
Ce.n.tfltin o WJMtd/UZLVaL Welt
06 Lwtd ç.LU
‘U
0
r-I
-3
tTj
DISTANCE PROM WELL (FT) = R
n
DISTRIBUTION OF GAS
METHANE GAS
Contoux& 4k0W concen-tiuttton o Pncthztne ga p’uLcx
to 4hon t-te.km pumpàtg.
-------
Ce.n teitIJ ne o WLdicL’tauiaL WvJ2
rop o Land U
E
p
T
H
F
C
E
L
L
Fr)
EflSTANCE FROM WELL (PT)
DISTRIBUTION OF GAS
METHANE GAS
Con.tow o 41ww c wtt a.tAo t o me.tjttxne ga4 a4tex
th 4kOfl. -Wun vump na.
100
-.#
SI4( RFrT n- R T( WAT. DADW
-------
DISTRIBUTION OF GAS
CARBON DIOXIVE GAS
100
Centei LLn o WA. .thdnawaL Well
Top 06 Land AJi
I . ’ )
D
E
p
T.
H
0
F
C
E
L
L
PT)
DISTANCE FROM WELL (FT)
Con.tou,’rA 6how con Qjvt,utt, op o civthorL dLox.tde
p’ .Loiz. .to 6hoiLt—.tvwl pwnpi t .
SHORFIL1Nc . REGIONAL PARI(
-------
SHORELINI . REGIONAL PARI(
100
C n e&LA n o WWtdi awo2 WeLt
Top Lcu’id/ iu1
D
E
p
T
H
0
F
C
E
L
L
:Fr)
DISTANCI FROM WELL (FT)
DISTRIBUTION OF GAS
C4 SCk VIOXIVE GAS
COfl t L t.c : .r t La_tl on o cwthon ckoxAde. ga
: - Z -t tn’ ru.
-------
Cen.teALLflt o WLthd’uwal WeU
op o La.nd6A12
C
E
L
L
YT)
‘., ‘I
n cr i
AT flAflLY
DISTANCE FROM WELL (FT) = R
DISTRIBUTION OF GAS
NiTROGEN GAS
Con.towt show conwitw t on c n t/wge.n
a4 pfl urn. -to 4ho’ - tQAM pamp. otg .
D
E
P
T
I L
0
F
i 00
-------
Cen-te,tUne o W kdiiawol WeLt
rop o La cL LU
0
E
p
T
U
0
F
C
E
L
L
:FT
DISTANCE FROM WELL (PT) = R
DISTRIBUTION OF GAS
JITRQGEfr GAS
C0n tou1L6 show con it 06 nAt’wgeii 9a4
jta hcn - j wrp .
100
SHORLLL\i-. REGIQNAL PARK
-------
D
E
p
T
H
0
F
C
E
L
L
FT) 100
SHORE1Jx . RFC 1 Iflr A!. p rn ’
So.ttom Lc td
FROM WELL (FT)=
DISTRIBUTION OF GAS
OXYGEN GAS
Con towt.6 4how onc n.t/tat,Lon o oxygen ga
jfl o4 to 4ho’ - te,rm pwnp- ng.
-------
Ccrt en tüte o W Wtd’ awa2 WeLL
Land
D
E
p
T
H
0
F
C
E
L
L
PT)
C
FROM WELL (FT)
I T ‘ • PARK
DISTRIBUTION OF GAS
OXYGEN GAS
ContouM 4 hOw conceyt tAa...tLon o oxygen a o it t€ ’ .
.ó tlOJL -teJun PWflP.LflcI.
-------
D
E
p
T
H
0
F
C
E
L
L
:FT)
\
Bottom o Lajtdt,4 Le
SHOR LI REGIONAL PARK
DISTRIBUTION OF GAS
METHANE GAS
G izph howo mo uemen.t 0£
a. ‘ u.U o 4ho t-.te,’un pumpiJtg.
100
Ceitte.t.A.n o WJ_tkd,w.wal WelL
rop o Land (J.iJI
P.’th /L to hott-. eJun pwnp.tng
A tvt o.4i- te.hJn pump.cng
DISTANCE FROM WELL (FT) = R
-------
D
E
p
1’
II
0
F
C
E
L
L
FT)
\
5o t.tom a Laitd AJ2
SHORELINI .. RF.GTflNAI. DARW
DiSTRIBUTION OF GAS
NITROGEN GAS
G’uiph. 4kow mov men t 0 9a4 aAS a.
4e4 u.U a ha’t.t- .teiun PWflP4n&1.
100
‘ - CQ,t €AZ . .ÜtQ oL WA.tItdi awaL We.U
rap o La.nd U
Pn . Lok .to 4ho .’ t-Wtin pwip .ng
fio’Lt-.tQJLn1 wflp.ot9
DISTANCE FROM WELL (FT) = R
-------
1 of 5
0MMENTARY
60
CornmQLrtce. £0fl9 /w.ng con itww
W4...tJ1dfl. awaL o £a d J Le ga
50
40
CONCEN-
TRATION
30
N 2
20
CH4
Co 2
10
0
DAYS
5
10
lb
MONTH
20
02
FEBRUARY
25
1975
30
LONG RANGE CONTINUOUS
GAS WITHDRAWAL CHRONOLOGY
30
PLATE 14
-------
2 of 5
Shwtdown
Low CH
DAYS
5
4
10
15
20
MARCH 1975
LONG RANGE CONTINUOUS
AS WITHDRAWAL CHRONOLOGY
Shwtdown Land LU hats
vio.t ‘LecoueJLed.
MONTH
25
30
31
PLATE 14
-------
COMMENTARY
60
50
40
Co 2
30
N 2
20
CONCEN-
TRATION
10
0
DAYS
MONTH APRIL 1975
LONG RANGE CONTINUOUS
GAS WITHDRAWAL CHRONOLOGY
3 of 5
4
%
:02
5 10 15 20 25 30
32
PLATE 14
-------
Anal y41.4 By
Ernc on A 4oca..te,
PG E ga o civtoma..togit.aph uI )LQpcLuJt o
50 c m
DAYS
5
10
MONTH
15
MAY ] 75
20
*Shwtdown ut t4zL&&on
o Low-Q Sy6tein
LONG RANGE CONTINUOUS
25
GAS WITHDRAWAL CHRONOLOGY
L ra e.d
,Le.4 wt 4
75 c m
30
33
PLATE 14
-------
AnaL y& 4 by PG E
5 of 5
%
CONCEN-
TRATION
S hwtdo t,n
k-Ji- H ; .
End LoI’L9 Range
Q thd&awaL o
Lctnd U Ga.o
50 c m
JUNE 1975
LONG RANGE CONTINUOUS GAS
Low-Ox Sy4tein WITHDRAWAL
Ev t io Rt iiL
if,
TT I ‘It TL1
H ±t -
---P
I T
1
f
H
itifi
I
COf ’J ME NTARY
60
5U
CU 4
40
Co 2
30
N
2d
10
0
—
H
t 1 T Th
-t-
—
CU 4
Co 2
N 2
02
DAYS
15
MONTH
20
Tn4taJ2a .t i .ori o
25 30
SHORELINE REGIONAL PARK CHRONOLOGY
314
PLATE 14
-------
HEAD = H
(- ins.
of
water)
SHORELINE REGIONAL PARK
DISTANCE FROM WELL (FT)= R
HEAD LOSS CURVES
‘ .r1
n j
C”
-------
HEAD= H
(— ins.
of
water)
SHORLLIM REGIONAL PARK
DISTANCE FROM WELL (FT)=
HEAD LOSS CURVES
1 of 2
a’
L X I
0
-------
HEAD= H
(— ins.
of
water)
HEAD LOSS CURVES
1
100 c m
2 of 2
Cwtve4 n.ep’Le.4en.t pe wte. head aLong
bottom o the !a.ndj,iJi when Land-
LU ga.o ..Lo w.Lthd’uzwn f iwm the m .ddLe.
o the Land A2L. See p.&euLou4 pLate.
o’t thdkau.v 2 /uUe4 g tea teiL than 100 c g3m.
La.nd 1 i2e Veptit
Re u4e Pe n4A..ttJ
Moi twLe
40 t.
1200 b/yd
20%
10
60
DISTANCE FROM WELL (FT)- R
SHORELINE REGIONAL PARK
-------
10
9 WZTHVRNiJAL RATE = 200 c u ,
CLL4Vt4 Mp4e4ent pte.ô4uXt kea.d aLong
8 .tke op(T),ni 4det(M),andbo.ttom(8)
o the Land d2 ii*en La.ndf, LU ga.4 L 4 s
7 ttu..thcLkau t hrn’? .the ni ddte o the £and 1 iJ2
a .C 200 c m.
6
Land 6A U Depth = 40 &t.
5 Re ws Veni J ty = 1200 £h/qd
Mos tw’Le 20%
HEAD H
(-
of
water) 3 ___ ___ ___ ___ ___ ___ ___ ___
2 __ __ __ __ __ __ __ __ __ __ __ __ __ __
- - - _
1 — — 1-— — _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____________________________
10 20 30 40 50 60 70 80 90 100
DISTANCE FROM WELL (FT)= R
HEAD LOSS CURVES
SHORELINE REGIONAL PARK
-------
50
WITHVRALML RATE = 200 c m
40 CWW€4 Mp/7J.hent pke.44uM he.c4 a2ong
the top (TJ, m Ldd e (M), and bottom ( )
o th £LUId ,U2 wkeit £a.ndé,AIL ga d(.4
wLthd aw,t tke bottom o tk £izndf,iJI
at 200 e m.
30
Land , LU Ve pth = 40 t.
R uoe fkn sJ ...ty = 1200 Lb/yd
HEAD = H Moi.. tuM 20%
- ins. 20 ___ ___ ___ ___
of
water) ___
10 ___ ___ ___ ___ ___ ___ ___ ___
-_______
M _ _ _ _ _ _ _
- - - ____ __
T 10 20 30 40 50 60 70 80 90 ioo
DISTANCE PROM WELL (FT)= R
HEAD LOSS CURVES
SHORELINE REGIONAL PARK
-------
in
1V AWAL RATE = 200 c m
Cwv.ue4 ‘Lep’Le.4e.nt pJ e44Wr.e ke d aLong
the. top (TJ, nu .ddk (14), and bottom (8)
o the. &utd i2t when Land Ut ga o 46
thd’cawn ‘zom the. nii4dtt and bot tom
o the. fjmd AU a.t 200 c. m.
DISTANCE FROM WELL (FT)= R
HEAD LOSS CURVES
9
8
7
6
5
4
HEAD= H
(- ins.
of
water)
2
Lo.ndf J2 Ve.ptit
Re. wSe. Ve.n4 tiJ
MoJ otuxe.
8
= 40 t.
= 1200 Lb/yd 3
20%
1
M
T
I I I
P1
w
10 2O 30 40 50 60 70 80 90 100
SHORELINE REGIONAL PARK
-------
9 WTTHVRALUAL RATE = 50 c. 4m
8 CLLIVt4 nip&eAent p e oou he.a4
aLon9 top (T), nu4dt...e. (M). and
bot2ou, (B) o the £cznd .LU wkcii.
7 Land. .U ao wi thdkawn jc.om
the bottom o the Zand6i...U a t 50 c m.
Land . IJL Ve.pth 40 t.
5 Re u4e. Veai 1200 ! b/yd 3
HEAD=H Moi . twte 20%
(— ins.
0 !
water)
2 ___ ___ ___ ___ ___ ___ ___ ___
1 __ __ __ __ __ __ __ __ __ __ __ __
____ - = =- - _ HI
r 10 20 30 4d’” 50 60 70 80 90 100
DISTANCE FROM WELL (PT) - R
HEAD LOSS CURVES
SHORELINE REGIONAL PARK
-------
0
F
100
flP1 T.T1Jk R1 r.TnNar DADV
D
E
p
T
H
C
E
L
L
Yr)
tTi
8o.ttom o Ce.U
WELL (FT)=
PRESSURE DIAGRAM
£o’ one - ndt wa teiz. pkeA4w con.towt. a.t d eM,L
w i tkd,LawaL ta.te s wke t !o.nd JJL ga6 .L6 tthdkawn
at Po.ôvt 5.
-------
C eiv eAL
-------
Head lo c.w ve. along the boLtom o
the I nd6.i . ..U when ex t1Lac tLng ga o iwm
the bo t.tom o the larid iJ1
1.0 Gevieka.l Fon.mala :
then 12.5/R 125 0k R 14
: and h - R/25 £° 0 R 14
whe4e
It .(.4 the he.ad along the boUorn
o 7 o tke Lzind LU a t 4onie. po4. n. t
d L4 ta.nt £kom the welt.
-co the head a.C the well
0.6
R Lo the dio ance £4om the weU
0.5
TA8LE OF VALUES
Rwku. .o h/t1 Rackws h/H
W 0.4
10 0.600 80 0.052
20 0.296 90 0.045
30 0.178 100 0.040
0 3 40 0.124 125 0.030
50 0.094 150 0.024
60 0.075 200 0.011
70 0.062 250 0.013
0.2 300 0.010
I _
0 50 100 200 300
DISTANCE FROM WELL (FT) = R
HEAD LOSS CURVE
SHORELINE REGIONAL PARK
PLATE 23
-------
60
HEAD =
(—ins. of
water) 30
20
10
0
50
Ge.nQ.n.aZ Fo/tmuia
H O.00039Q(Q÷133)
• Expeit m n taL PoLi t t4
40
100
WITHDRAWAL RATE = Q(cfm)
DISCHARGE RATING CURVE
WQ U
Lok
O £c.nd iJ2
SHORELINE REGIONAL PARK
7A 4.?hen w Lthdiiawi ..ng c t bot om
45
PLATE 24
-------
300
*Deriyed empirically,
ACCURACY OF RESULTS
1’Jo0
250
200
150
a’
CHARGE
(cfm) = Q
100
50
AcclmLleq
jR€4LLU6 Sq A’Lea *
DISTANCE FROM WELL (PT) = R
I. Accwuzte
2. S1 gkUq e. jecL d bq €nu L&onmen , p’c 4áwLe4 mea4uAab t
3. E ected by env uwnme,vt, on4A ten.t mz e,nvt
4. P4e 4cme. s too Low to mea4w e
5. lmag.àiaMj
SHORELINE REGIONAL PARK
-------
—
SHORELINE REGIONAL PARK
- -
- -—- __.; --—--: ‘ -- • -
•: - - ‘-; • : - ,
.d 0
-
-------
MONITORING BUJLVING
LAP4VF1LL
MER
VOLKSWAGCN
ENGINE
LA IV FiLL GAS
TO PUMP
PUMP
TRAJPISMISSTON
LMVF1LL GAS PRESSORE
“,
VOLKSWAGON ENGINE AND PUMP
PARK
SHORELINE REGIONAL
-------
EL
U )
I - I
p -3
0
I - I
z
C
1 1Th
w..
‘ : rr :
I
-
U
am
U
¼0
/
4’
U U .
a
a
a
a
S
SHORELINE REGIONAL PARK
‘4.
S.
-------
.SPARK PLUG
FLAT PLATE
IN.SIVE BURNER
TO MIX AIR AND
GAS\
:9.
WINV BARRIER
,ENGINE COIL
A ____
0
C)
LT1
PLATE TO VARV
AiR MIXTURE
—-t
LANVFI
BURNING
PUMP
IR iNTAKE
STACK
-------
APPENDIX
51
-------
PART A - PROBLEMS, DELAYS, AND CHANGES
Problems and Delays
No company had three pumps available for immediate delivery, and we were
faced with a 3- to 8-month waiting period for fabrication. It took 2 weeks of
calling to different manufacturers to get 3 pumps that matched our specifica-
tions and were in stock.
There was an 8-month delivery date for electrical motors and a 2—month
delivery date for a gasoline engine. Therefore, Volkswagon engines were chosen
since they had the right horsepower range and are air cooled.
The piping for the withdrawal wells had a 10—week delivery date which was
the shortest time that could be found. The monitoring equipment had a 2-month
delivery date.
Due to requirements of the City of Mountain View Charter, construction of
the station had to be opened to competitive bidding. Normal scheduling would
have delayed the project Into winter and could have delayed the project for
6 months; however, the scheduling was shortened to 1-month which allowed con-
struction to proceed prior to winter.
Testing prior to the Initiation of this project indicated that an inter-
nal combustion engine would run on refuse gas; however, there were problems
with keeping the Volkswagon engine continuously running on the refuse gas.
The problem appeared to be the spark plugs and/or the regulator, but the prob-
lems were never solved and gasoline was used to fuel the engines.
Preliminary tests proved that the refuse gas could be ignited in the burn-
ing stack by a spark plug situated on the side of the stack. The spark plug
would receive impulse charges from a coil that was connected in series with
the coil for the engine which ran the pump. However, when the same arrangement
was installed using the Volkswagon engine, the second coil lowered the energy
output of the engine coil which resulted in the fouling of the engine spark
plugs. An electronic vibrator (run off the engine battery) has been substi-
tuted for the points in the engine and is providing impulse charges, via a
coil, to the stack spark plug. This system kept failing and an adequate sys-
tem was never obtained.
The landfill gas was at or near saturation levels and the water in the
gas caused many problems. By placing a demister in the line prior to the
Volkswagon engine, it alleviated the problem of water accumulating in the pres-
sure regulator. The demister was a 55-gallon drum stuffed with fiberglass
screening. The gas was pumped Into the drum, which stood on end, at the bot-
tom, tangentially, and exited out the top in the middle of the flat end. The
water also collected in the pressure monitoring tubes that lead to the moni-
toring board. The lines had to be continually cleared before pressure mea-
surements could be made. To avoid the water collecting in the pipes from the
wells to the pumps, the pipes were sloped back to the wells.
52
-------
Changes
From the second interim annual report of the Sonoma County Refuse Test
Cells , Solid Waste Disposal Demonstration Grant, Project G06-EC O035l, pre-
pared by EMCOP’J Associates, it is shown that the leachate pH is contaminated
by soluable gases, especially carbon dioxide, and remains around 5. When the
leachate was sampled from the collector at Well 7A, it was found to be 4.6.
This indicated that the conditions were similar to the test cells in Sonoma
and that the pH would not be a good indicator of the change of digestion pro-
cesses in the landfill. Therefore, scheduled testing of pH was discontinued.
From the report mentioned above, it was apparent that more information
about the gas production could be obtained by a continual complete analysis
of the refuse gas as it was being pumped from the landfill. The following
testing procedure was added prior to the coum encement of the pumping.
a. Prior to initial pumping at all 4 wells, a complete gas
analysis was made at each production well point and pres-
sure point.
b. During pumping a complete analysis of the gas was made
twice a day, at 10 a.m. and 3 p.m., twice a week.
c. After the short-run testing was completed, the procedure
in a. above was repeated.
ci. During long-range pumping, a complete analysis was run
twice a week, i.e., on Tuesday and Friday.
e. After the long-run test was completed, the procedure in a.
was repeated.
53
-------
PART B - DATA
Testing on production Well 7A started on December 10, 1974. From Decein-
ber 10 through December 12, gas was sampled from each pressure point and well
point and a complete analysis was run.
From December 15 through December 26, gas was pumped from the deep well
point at 100 cfm, 150 cfm, 200 cfm, and 300 cfm. From January 6 and 7, gas was
pumped from the shallow well point at 100 cfm, 150 cfm, 200 cfm, and 300 cfm.
From the test results from December 15 through January 9, it appeared that the
best pumping rate might be 200 cfm; so on January 9, gas was pumped from both
the deep and shallow well points at 200 cfm. After the short-run testing on
January 17, gas was sampled from each pressure point and well point for the
monitoring Well 7A and a complete analysis was run.
On February 11, 1975, the long-range continuous pumping started. The Ini-
tial pumping rate was 200 cfm, and the gas was withdrawn from the bottom of the
landfill. Plate 14 shows the results of the pumping. The withdrawal rate was
continuously lowered until a steady composition was obtained at 50 cfm,
All gas analyses for the above follows.
5 4
-------
PART C - GAS DYNAMICS IN THE SANITARY LANDFILL
The refuse chamber is sealed on the bottom and sides by 5 feet of clay
and on the top by 1 foot of clay. The clay has a permeability to water of at
least iO’ 7 cm/sec. The area around Well 7B has 1 foot of clay while the area
around Well 7A has an additional 2 feet of similar clay with some sludge mixed
into It.
Reference Is made to the State of California Water Quality Control Board
publication entitled, “IN-SITU Investigation of Movements of Gases Produced
from Decomposing Refuse,” dated 1965, prepared by Engineering-Science, Inc.,
Oakland, CA. In the report, the following equations are given for diffusion
of gases through soils:
CD
q P Al
L
D
= O.66P A2
Do
Where q = net transfer rate in feet per day.
= gas concentration in top layer of landfill in fraction by volume.
diffusivity of a gas in soil in square feet per day.
= diffusivity of a gas in free space in square feet per day.
L = thickness of soil cover in feet.
P = porosity of soil cover as a ratio.
55
-------
The transfer rate will vary using the temperature, pressure, and the gas.
Using the following reasonable assumptions taken from this report and our data,
Temperature = 68°F
D 0 (C0 2 ) = 15 sq.ft./day
D 0 (CFI 4 ) 20.7 sq.ft./day
Porosity = 30% (60% porosity - 30% moisture)
C (C0 ) = 30%
C (CH 4 ) = 35%
and
D
P 0.66P = 0.198
D
0
the following calculations for the diffusion rates for methane and carbon diox-
ide can be made.
for CU 2 : q ( .30) (15 ft. 2 /day) (0.198 )
CO 2 3ft
= 0.297 ft./day
2
for 1 acre: (0.297 ft./day) (43560 ft. /acre) (1 acre)
2 (1 day/24 hours) (1 hour/60 mm.)
= 8.98 cu. ft./min.
for CH 4 : q = ( .35) (20.7) (0.198 )
4 3ft.
= 0.478 ft./day
4
for 1 acre: CH = (0.478 ft./day) (43560 ft. 2 /acre) (1 acre)
4 (1 day/24 hours) (1 hour/60 mm.)
=14.46 cu.ft./min.
56
-------
Therefore, for every acre of landfill, methane, and carbon dioxide gases
will diffuse through the seal at a combined rate of approximately 23.4 Cu. ft.!
mm. It is important to realize that diffusion does not require a pressure
head. Therefore, when the barometric pressure Is dropping, the extracellular
pressure Is lower than the intracelluar pressure, and additional landfill gas
Is forced into the atmosphere. When the barometric pressure is rising, the
extracellular pressure Is greater than the intracelluar pressure and the dif-
fusion will not stop until sufficient pressure head is developed to reverse
the flow.
As a side note, nitrogen and oxygen are in greater concentration in the
atmosphere than in the landfill; thus diffusion of these gases into the land-
fill occurs. A rise in barometric pressure aides the diffusion and a drop in
barometric pressure reduces or negates the diffusion effect.
In an attempt to verify in the laboratory, the porosity of the clay seal,
a 6-inch plastic pipe with 3 feet of compacted clay in it was subjected to
minus 2 inches of water pressure. Within 15 minutes, the pressure had dissi-
pated. The flow was too low to measure with our Instruments which can measure
to a 0.1 standard cu. ft./hr. which is 72.6 Cu. ft/mm. per acre.
climatic Influence
The Department of Commerce in Oakland has indicated that the barometric
pressure In the Bay Area has a seasonal variance from 30.5 inches of mercury
(414.80 inches of water) to 29.5 inches of mercury (401.20 inches of water)
with a mean of 29.92 inches of mercury (406.91 inches of water). The average
rate of change in barometric pressure is 0.08 inches of mercury (1.09 inches
of water) per hour with a maximum rate of change of 0.1 inches of mercury
(1.36 inches of water) per hour. The rate of change in pressure could be
faster; however, the mountain ranges surrounding the Bay tend to disturb and
mix weather fronts as they move into the Bay.
TABLE Al
Static Pressure Readings
Taken on 11/22/74 around Well 7A
Time A.M. P.M.
Barometric
Pressure (BP) 410.60 ins, of H 2 0 410.19 ins, of H 2 0
Intracel 1
Pressure UP) 410.60 ins, of H 2 0 410.23 ins, of H 2 0
(Average)
(BP) - UP) 0 -0.04 ins, of 1120
57
-------
Table Al summarizes the information in which it can be seen that the
average landfill pressure adjusted to the changing barometric pressure except
for 0.04 inches of water. The account for the equalization of pressure; the
landfill is either changing in volume or the air and landfill gases are moving
through the top clay seal which is 3-feet thick. From the Information given
In the previous part of the Appendix, it is evident that the landfill is
breathing. Since the pressure equalization effect pertains to the full depth
of the landfill, there Is movement of gas even at the bottom of the landfill.
Table A2, at the end of this section, provides a partial picture of the
effect the barometric pressure has on the gas extraction. The figures in
Table A2 show that as the atmospheric pressure dropped, the negative pressures
In the landfill Increased. The pump is withdrawing gas at a negatIve 6 Inches
of water pressure at the bottom of the landfill at the well head designated 7Ad.
The atmosphere is applying a gradually increasing negative pressure of 0.95
inches of water pressure from 5 p.m. to 9 p.m. With the atmospheric pressure
dropping, pressures should increase positively In the landfill if air is not
moving through the top seal. However, Table A2 shows that the atmosphere is
competing with the pump for the landfill gas and resulting higher negative
pressures are realized in the landfill.
As further evidenced, when Well 7A was pumped at 200 cfm, the nitrogen
level inceased from 13.65% to 39.98% in the extracted landfill gas. A com-
parison of several points in the landfill is shown in Table A3.
TABLE A3
Percent of Nitrogen BEFORE/AFTER pumping at 200 cfm
DI stance
from Well: 15’ 30’ 60’ 100’
Top of Landfill 28.98/79.73 58.23/84.83 42.59/79.27 61.98/63.63
Bottom of 2.51/10.99 8.51/41.06 27.93/58.05 5.80/34.81
Landfill
The data In Table A3 clearly indicates that air, represented by the
amount of nitrogen, was drawn into the landfill over a wide range of the
landfill.
58
-------
TABLE A2
PRESSURE READINGS (Ins, of H 2 0) WHEN WITHDRAWING
LANDFILL GAS AT 75 CFM FROM WELL HEAD POINT 7Ad
Change
Time: 5 p.m. 6 p.m. 7 p.m. 8 p.m. 9 p.m.
Barometric 1 408.95 408.41 408.14 408.14 408.00 -0.95
Well Head
*Sha l low _7ASM 1 -0.11 -0.13 -0.16 -0.26 0.29 0.18
Middle -7As -0.29 -0.32 O.36 -0.50 -0.51 -0.22
Deep -7Ad _6.0** -6.0 -6.0 _6.0**
At 15’ from Well Head
Sha llow-7AM1S 0 -0.10 -0.25 -0.43 -0.31 -0.31
Middle -7AM1M -0.39 -0.44 -0.47 -0.58 -0.63 -0.24
Deep -7AM1D -3.48 -3.60 -3.70 -3.75 -3.84
At 30’ from Well Head
Shal low-7A142S 0 0 -0.15 -0.22 0.26 -0.26
Middle -7AM2M -0.24 -0.28 -0.32 -0.45 -0.48 -0.24
Deep -7AM2D -1.34 -1.41 -1.49 -1.58 -1.63
At 60’ from Well Head
Shallow-7AM3S 0 0 0 0 0 0
Middle -7A1.13M -0.23 -0.28 -0.3 -0.44 -0.49 -0.26
Deep -7AN3D -0.41 -0.48 -0.52 -0.65 -0.69 -0.28
At 100’ from Well Head
Sha llow-7AM4S 0 0 0 -0.28 -0.31 0.31
Middle -7AN4M 0 0 0 0 0
Deep -7AM4D -0.04 -0.08 -0.08 -0.26 -0.28 -0.24
At 200’ from Well Head
Shallow—7AM5S -0.41 -0.38 -0.45 0 -0.39 +0.02
Middle -7A1 1SM 0 0 0 0 0
Deep •7AN5D +0.19 +0.14 +0.02 0 -0.75 -0.94
*Refer to Plate 2 for visual location of well points within landfill.
** Adjusted Pressures
Actual Pressures are:
5 p.m. -6.2
8 p.m. -6.4
9 p.m. -6.1
Pressures in these columns adjusted by percent so that
comparison can be made.
59
-------
PART D — LO-OX INDUCTION SYSTEM
Air entering the landfill is limiting the amount of gas that can be
removed from the landfill from a vertical well. If the amount of air can be
reduced or eliminated, increased gas production should result.
Air enters the landfill through diffusion and pressure. Diffusion will
only stop if concentrations on both sides of the top seal are equal or when
pressure within the landfill offsets the diffusion of air into the landfill.
Both solutions are incompatible with the current method of withdrawal. There-
fore, diffusion will occur and adjustments would have to be made in the clean-
ing facilities to allow for this air.
Air entrainment via pressure differential across the top seal can be
stopped. The present procedure withdraws the landfill gas at a rate which
creates a slightly negative pressure just under the top seal. When the
atmospheric pressure is constant, increasing, or very slightly decreasing,
air will enter the landfill due to the negative pressure in the landfill.
The suggested approach to relieve the negative pressure is to recycle
some of the extracted gas, called LO-OX because of its low oxygen content,
through an upper-cellular pressure equalization system, UPES. The UPES will
consist of piping leading from the positive pressure side of the withdrawal
pump to the refuse/top seal Interface. Valving would allow the LO-OX gas to
enter the piping at the pump at a little above atmospheric pressure. The neg-
ative pressure at the Interface would draw the LO-OX gas through the pipes
and into the landfill. The horizontal stratification of the refuse would
allow the LO-OX gas to expand horizontally and effectively reduce the amount
of air entering the refuse.
By introducing LO-OX gas at the refuse/top seal interface, the amount of
oxygen and nitrogen entering the landfill is reduced. For instance, without
LU-OX gas, air entering the landfill contains 80% nitrogen and the extracted
landfill gas contains 20% nitrogen. If this LU-OX gas is recycled using UPES,
the LO-OX gas with 20% nitrogen would replace air with 80% nitrogen and a
landfill with a lower nitrogen content would be obtained. Nitrogen cannot be
completely removed, however, due to diffusion.
This system was installed at withdrawal Well 7A but no substantial test-
ing was done.
60
-------
PART E - COSTS
For informational purposes, the following are costs related to the project
n 1974 dollars.
1. 3 Positive Displacement Pumps, 200cfm $2500 (total)
2. 3 Volkswagon Engines, assembled $2800 (total)
3. Complete Pumping Station* $4400 (total)
4. Complete Extraction Well $13.00/ft.
* Include grading, concrete pad, monitoring shack, fencing, and internal piping.
61
-------
PART F - CALCULATIONS
Total Gas Production Rate
——0—
\
\
\
\ /
\/
I
\—
,1
\
\
I\
i__i - - —
t 1
V
/ N
1) Well Spacing
S = 2a 2(r cos 30°)
= (2)(130 ft..)(O.866)
S = 225.17 ft.
w
— —
,
V
I
I
- .-
I
(- -F--
‘I
/
/
——0—- —
I
\ /
/
N/N
/ ..—--——
\
/
/
/
\
/
/
k
/
/
— — —. —
Figure Fl
62.
-------
2) Withdrawal rate per acre is based on one half well per
base triangle with sides equal to 225 ft.
a) Triangle Area, At
At = ½S (r + b) ½S (r + a tan 300)
= (½)(225 ft.) (l3Oft. + (112.5ft.)(0.577))
At = 21,932.09 ft. 2
b) Withdrawal Rate/acre, acre
43560ft. 2 /acre
acre - wel1 At
= (½) (SOcfm) ( 43560ft. 2 /acre )
21932ft.
acre = cfm/acre
3) Total Site Production, site
site = acre”site
= (49.7 cfm/acre) (150 acres)
site = cfm
or
- ( 60 min.L (24 hrs.) — l macfm )
‘site (455 ) (1 hr.) (1 day) (1,000,000 cfm)
site = 10.7 inmcfd
63
-------
legion I
.ohn F. Kennedy Bldg.
Boston, MA 02203
(617) 223-7210
Region SI
26 Federal Plaza
New York, NY 10007
(212) 264-2515
Region Ill
6th & Walnut Sts.
Philadelphia, PA 19106
(215) 597-9814
Region IV
345 Courtland St., N.E.
Atlanta, GA 30308
(404) 881-4727
Region V
230 South Dearborn St.
Chicago, IL 60604
(312) 353-2000
Region VI
1201 Elm St., First
Dallas. TX 75270
(214) 749-1962
Region VII
1735 Baltimore Ave.
Kansas City, MO 64108
(816) 374-5493
Region VIII
1860 Lincoln St.
Denver, CO 80203
(303) 837-3895
Region IX
100 California St.
San Francisco, CA 94111
(415) 556-2320
Region X
1200 6th Ave.
Seattle, WA 98101
(206) 442-5810
International Bldg.
U.S. ENVIRONMENTAL PROTECTION AGENCY
Regional Offices
iia1516
SW—587
MJ.S. GOVERNMENT PRINTING OFFICE: 1977 720-11615712 1-3
------- |